This invention relates, in general, to fluid heater apparatus and, more particularly, to fluid heater apparatus which provides a heated wash fluid to a cleanable surface, and, still more specifically, to a heated wash fluid apparatus for a vehicle windshield wash system.
It is necessary in many diverse applications to quickly elevate the temperature of a fluid to a higher use temperature. For example, it is desirable to be able to provide instant hot water, for use in homes, offices and campers, as well as for industrial processes.
In cleaning applications, it is known that hot fluid removes dirt and other debris from a surface much better and much faster than colder fluids. One heated fluid application is a vehicle wash fluid system, such as a windshield wash system as well as vehicle wash systems applied to camera lenses, exterior lamps and lamp lenses, mirrors, etc. Vehicles are typically provided with at least one and usually multiple windshield washers which are used to clear the field of vision in a windshield or rear backlight.
Typically, a nozzle or spray device is provided adjacent to or as part of the windshield wiper to disperse a pattern of wash fluid onto the windshield prior to and during the wiping operation to improve the efficiency of the wiping operation so as to provide a clear field of vision for the driver or vehicle passengers. The wash fluid is typically stored in a reservoir in the engine compartment and is pumped through the spray device upon manual activation of a control actuator by the vehicle driver.
Since it is known that warm or heated fluid provides better cleaning efficiency than cold fluid, it is known to provide a heated wash fluid to a vehicle window spray device. Various wash fluid heating devices have been developed, but all typically utilize a heat exchanger design wherein a heat source is disposed in a body through which the wash fluid flows. The wash fluid picks up heat in the heat exchange body which elevates its temperature prior to dispersion through the spray nozzle onto a vehicle window.
A vehicle wash device is subject to a wide range of temperatures and types of fluid. It is possible and fairly common that consumers may use only water as a vehicle wash fluid. However, at sub-freezing conditions, this may result in damage to the fluid storage device due to expansion caused by the phase change of water to a solid state. The resulting damage may cause leaks, fractures, yield of materials, or a general malfunction of the fluid heater.
Thus, it would be desirable to provide a fluid heater apparatus providing a heated fluid which has fluid freeze protection. It would also be desirable to provide a fluid heater apparatus which provides freeze protection without a substantial increase in the number of components employed in the fluid heater apparatus.
The present invention is a fluid heater apparatus with unique freeze protection means. The freeze protection means reversibly allows expansion of the fluid in the fluid heater when the fluid undergoes a phase change to a solid or semi-solid state and is reversible to a normal state overlaying the fluid flow channels when the fluid undergoes a phase back to a liquid state.
In one aspect, the heater apparatus includes a thermally conductive mass, heating means thermally coupled to the thermally conductive mass for imparting heat to the thermally conductive mass, and a fluid flow path formed in the thermally conductive mass between an inlet and an outlet. Fluid in the fluid flow path absorbs heat from the thermally conductive mass.
In one aspect, the heater apparatus further includes a fluid expansion means carried in a closure carried on the mass for reversibly allowing expansion of fluid in the fluid flow path when the fluid undergoes a phase change to a solid state.
In one aspect, the fluid expansion means is in the form of a compressible member which may be formed of a closed cell foam. The compressible member is disposed in an enlarged interior chamber formed in the closure or plate attached in the thermally conductive mass and overlays the ends of the fluid flow channels in the thermal mass.
In another aspect, the present invention is a wash apparatus including a fluid reservoir contain a wash fluid, a pump coupled to the fluid reservoir for pumping fluid from the reservoir, a spray nozzle fluidically coupled to the pump for discharging fluid pumped from the reservoir onto a cleanable surface, and the heater apparatus disposed in fluid flow communication between the pump, the reservoir and the nozzle.
In this aspect, a fluid expansion means carried in the closure for reversibly allowing expansion of fluid in the fluid flow path when the fluid undergoes a phase change to a solid state.
The fluid expansion means may also be provided with fluid flow apertures which allow fluid flowing through a portion of the fluid flow channels in the thermal mass to flow through the fluid expansion means and impinge against the inner surface of the closure on the thermally conductive mass. This enables heat to be removed from the high heat generating power switch elements mounted on a circuit board on one closure as well as allowing fluid to impinge more closely on the portion of the closure on which the thermal sensor is mounted to provide a more accurate temperature measurement of the fluid of the fluid heater apparatus.
In another aspect of the invention, a fluid expansion means is provided by the seal members having a solid shape overlaying substantially all of the open ends of the fluid flow channels on one surface of the thermal conductive mass. Each seal member has sufficient rigidity to resist expansion or movement when exposed to the normal operating pressures of the fluid flowing through the fluid flow channels. However, expansion of the fluid in the channels caused by the change of phase of the fluid to a solid or semi-solid state exerts sufficient pressure on the seals to cause the seals to expand into an adjacent open interior cavity formed in the closure to accommodate the fluid phase change expansion. The seals assume their normal generally planar shape when the fluid changes phase back to a liquid state.
The fluid heater of the present invention has a unique freeze protection means which accommodates phase change expansion of the fluid in the fluid heater when the fluid transitions to a semi-solid or solid state, but is capable of returning to a normal shape and position overlaying open ends of the fluid flow channels in the thermally conductive mass when the fluid reverses phase to a liquid state.
The fluid expansion means is easily accommodated in a fluid heater apparatus with minor modifications.